This invention relates to navigation systems and, more particularly, to a navigation system and method for improving reliability of estimating a navigation system solution.
Navigation devices are widely known and used in vehicles, hand held devices, and other devices to indicate location and for route guidance. Often, such devices include a screen for displaying a map and indicating a current location on the map. Typically, a conventional navigation system utilizes dead-reckoning to determine the current location. Although methods of dead-reckoning vary, dead-reckoning may entail, for example, estimating the current location based upon a previously estimated location, speed, direction, and time. Typically, the current location is then matched with a database map to determine the current location with respect to roadways or other landmarks. This distance off the roadway and the heading of the roadway may be used as an additional piece of data in determining the current location and heading.
Conventional navigation devices are not always able to reliably estimate the current location. For example, such devices usually require some time to start-up after being turned on. During start-up, the navigation device cannot perform any navigation computations because it is occupied loading the operating system, transferring files, initializing hardware, etc. Furthermore, GPS location and heading may be unavailable even after the start-up is completed. As a result, when the navigation device begins dead-reckoning, the estimation of a new current location and heading may be unreliable.
Accordingly, there is a need for a navigation device that is capable of performing dead-reckoning functions while the navigation device is occupied with other activities such as boot-up.